1. Field of the Invention
The present invention relates in general to nozzles for use in an injection molding system. More particularly, the present invention relates to an improved injection molding nozzle characterized in particular by minimal heat loss characteristics and an improved sealing technique.
2. Discussion of the Related Art
A common problem in the field of injection molding is the need to keep the melt that forms the molded article at a uniform temperature as it passes from a plastic melt source through an injection nozzle and into a cavity in the cooled mold. The melt is uniformly kept at its optimum melting point in order to assure a good melt flow. The optimum temperature is the temperature at which no melt freeze-off or burning occurs.
Usually, a bore is formed in the cooled mold in which the nozzle is seated. The mold is often several times cooler than the melt, thus, in order to keep the melt at its optimum flowing temperature, the nozzle is heated by heating coils, heat pipes, electric resistance heaters, or other appropriate heating means. As the nozzle is surrounded by the cooled mold, significant heat loss can occur between the nozzle and the mold which can affect the temperature of the melt. Further, the heat transfer from the nozzle to the mold can affect the solidifying times of the molded article in the cavity within the mold. Accordingly, there is a need to provide effective insulation of the nozzle within the mold to minimize heat loss from the nozzle to the mold.
In view of the foregoing, it is an object of the present invention to provide improved insulation of a nozzle for an injection molding machine, in order to minimize heat loss that occurs from the heated nozzle to the cooled mold.
Another object of the present invention is to provide an improved nozzle seal that provides, not only the aforementioned heat insulation characteristics, but also a simple and effective seal against melt leakage from the gate.